Praseodymium-core carbon rods.
Rods like this (about 1/2" diameter) are used, or at least used to be, in the motion picture industry to create large amounts of light for filming. They contain a core (visible in this photo) of a mixture of rare earths which, when vaporized in the arc, provide a daylight spectrum of light. This use is very similar to the way the rare earths provide daylight spectrum light in modern sealed arc lights, just out in the open air.Source:eBay seller saturngroupContributor:Theodore GrayAcquired:16 April, 2009Text Updated:17 April, 2009Price: $22/boxSize: 12"Purity: <20%